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Research Grade Telecentric Unit, featuring an oversized pick up expanding lens set and 2" (50.8mm) threads on both sides – T-2 Adapter and 2" m/f inverter ring are both included as standard accessories

46mm clear aperture at the H-alpha-filter entrance side - suitable for research grade SolarSpectrum H-alpha filters

Large working distance of 250mm for optimized focal length reduction with a telecompressor and suitable room for adapting a binocular viewer

Aplanatic, with 3x focal length extension to achieve a parallel f/30 beam in conjunction with ~f/10 optics systems – free of field curvtare

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If using the TZ-3 with a 32mm CA SolarSpectrum ASO model is some light lost since the TZ-3 is designed to produce a 46mm output beam? If 'yes', light is lost, when used with a 32mm etalon can the rear lens of TZ-3 be moved closer to the front / input lens to produce an exit beam more closely matched to the 32mm CA of the ASO model Ha filter and thus produce a brighter image in an eyepiece?

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Question by: Anthony Sarra on Mar 12, 2017 7:25:00 AM | 1 Answer(s)

There is no light getting lost when using the TZ-3 on smaller sized etalons. In fact the TZ-3 offers the very same brightness with even a 19 mm sized etalon than the TZ-2 and TZ-4 - but the latter two simply are not able to cover the large field of a 46 mm etalon - like we offer in form of the research grade SolarSpectrum filters. All these three TZ-systems have a very similar focal length design, ranging between 200 to 250 mm. TZ-systems optically work best at such long FLs. We checked many optical designs to ultimately decide for these long FL-solutions. Trying to shorten the mechanics of the TZ_3 (or shortening on the FL) in any way will always result in a severe loss of optical performance.

We have analyzed the optics inside the Quark for instance - and we must be too stupid maybe, but according to our calculation the resulting monochromatic spot diagrams look horrible. So yes - you certainly can try to trim down the TZ-optical principle in terms of shorter FL and small lens sizes. But we conclude that a lot of contrast (and image brightness) goes bust that way. So please do not try to move inward the exiting lens on the TZ-3 - the optical quality will be gone - and the warranty too.

Better look into the solar telecompressor 0.4x that we had designed to work perfectly with the TZ-3. The image will be "very bright" as you end up with an f/10 beam when the incoming FL was set to f/10 as well.

We will continue to look for alternative optical solutions for small etalons, but certainly it must be way better than what we find in the market right now.

A couple of followup questions. 1) I noticed the TZ-3 tube has 3 'sections' longest being in front, shortest at rear holding 'collimation'/'pickup' lens and a middle section that appears to be just a spacer. Can the middle section be removed (omitted) such that rear lens becomes closer to front 'input' lens.
2) Is the middle section intend for removal to provide for an alternate closer location of pickup lens or is this just a manufacturing convenience to be a separate part (reuse of existing parts?)?
3) What would be the characteristics of the resulting output beam? Diameter, F#, impact on position of TZ relative to main objective (assume that would not change), impact on distance from TZ to final focal plane which was originally 250mm?

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Question by: Anthony Sarra on Mar 12, 2017 8:05:00 PM | 1 Answer(s)

This definitely is not the case. Neither the TZ-3 nor any other TZ-system can retain its designed optical performance, when the distance between the internal lens groups is being altered.

Answers for individual questions:
1) The middle intersection roughly marks the position of the initial instrument focal length. The middle section cannot be removed.
2) The middle intersection bears a mask (straylight shield). No part of this product is being "reused" on any other product.
3) A large deviation from the designed 250 mm focal lenght is not advisable. Noticeable deterioration of the image contrast would be inevitable.

Can the Baader Telecentric lenses be used like ordinary Barlows, e.g. for visual observation or imaging (from UV to IR) of the planets?

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Question by: Jack on Feb 10, 2017 7:21:00 AM | 1 Answer(s)

A Telecentric is not a Barlow, although it also affects the focal ratio. Its main purpose is to produce a beam of parallel light for H-alpha-filters. The change of the focal ratio is only a side effect.

Because they are made for H-apha-filters, they are designed for 656.3 nm (the red H-alpha-light); only the TZ3 is also designed to work at 396 nm very good, although then the focal plane is shifted for ca. 5mm.

For visual observations in other parts of the visual spectrum, you need a Barlow, not a Telecentric.

Details

Baader Telecentric Systems for focal length extension

for supplying a parallel optical beam and for providing sufficient backfocus, in conjunction with any SolarSpectrum H-alpha filter

Telecentric optics sets are often confused with a barlow lens. Both can be used to increase the focal length. Telecentric assys are designed so that the exit pupil seemingly is positioned at infinity, which means that the center ray from any point in the field appears to come from infinity and is therefore perpendicular to the image plane and parallel to the optic axis. This means that the off axis beam does arrive at the image plane with the same angular geometry as the axial rays. All field elements look as if they where on axis, across the image plane and - unlike to a barlow lens - the edge field rays are not tipped bundles.

Because all the principal rays across the image plane are perpendicular to the image plane, the rays at the edge of the field will pass through an etalon just in front of the focal plane with exactly the same geometry as the rays on axis. So in an f/30 telecentric optical arrangement, the etalon sees the exact same geometry clear across the field, and the spectral bandpass does not shift in wavelength across the entire field of view.

Starting from an aperture ratio of ~f/15 (+2x Telecentric), ~f/10 (+3x Telecentric) or ~f/7.5 (+4x Telecentric), the Baader TZ-systems will create a parallel beam with ~f/30 aperture ratio. In the case of largely deviating telescope focal lengths, the clear objective aperture of the telescope should be reduced in diameter to the point that the final resulting f/ratio is close to f/30 again (we do offer a suitable iris-diaphragm for this purpose).

TZ-system working distances – when measured from their rear lens – range from 200mm for the TZ-2 to 230 mm for the TZ-4 - to 250 mm for the TZ-3. This provides enough room for the H-alpha filter housing and most any accessories, e.g. a Baader 2" mirror diagonal or any conceivable camera device. The generous room of the TZ-3 will also accommodate a binocular viewer when it is mounted onto the SolarSpectrum body by means of a Baader BBHS T-2 star diagonal. All TZ-coatings are matched to the different lens glass-substrates and optimized for maximum throughput at 656 nm. Still the TZ-3 especially also works for CaK at 396 nm. The TZ-3 Strehl-ratio is well above 80% at 396 nm

Please also note the detailed PDFs under the Tab "Downloads" for further information

Related Articles

Related Articles

An experience and observation report on the new Baader Telecentric System TZ-3 and the Research Grade (RG) Telecom­pressor (TC) 0.4 for solar observation in the H-alpha light with SolarSpectrum filters
download the complete review (pdf)
Introduction
Successful H-alpha-observations of the sun with narrow-band line filters from the manufacturers “SolarSpectrum” and / or "DayStar" require an almost parallel beam of light with a focal ratio of approx. f/30 directly in front of the filter, otherwise the filter will not work properly. This is not so easy with today's fast optical systems, which work around f/7. Such an opening ratio can be achieved either by masking (reducing) the front lens opening or by parallizing the optical beam with a "telecentric system" (TZ). * TZ: See also the supplement at the end of the report.
My "solar telescope" is an AstroPhysics refractor with an aperture of 155mm and a focal length of 1.085mm, the aperture ratio in the prime focus is f/7.
In order to use the filter without extending the focal length, the telescope's aperture would have to be reduced to approx. 35mm in order to realize the optimum f/30 focal ratio. It is clear that this is highly unsatisfactory – the resolution detail...

My solar instrument consists of the following parts: first a full aperture Baader ERF filter, next a refractor Orion 100/1000, next a blocking filter, next the TZ3 telecentric system, next the central part of Daystar Quark filter (in fact the Ha interferentiel filter), next a diagonal mirror, next a tilter to avoid fringes in the image and to finish ZWO cmos camera. So the total focal is 3000mm, giving a solar image size of about 27mm. The refractor is in parallel with my 300mm Meade SCT on an homemade azimuthal mount.

The system can be used in visual too, by removing the camera and place an eyepiece.
The first notable thing in visual observation is the contrast of images: it's a lot better than with the previous telecentric barlow included in the Quark. The image is sharp in all the field of view. The Fabry Perrot filter seems to work fine with the quasi-parallel rays comming from the TZ3.
With the camera, it’s mandatory to have a tilter, otherwise you have fringes due to interferences. And again the images after processing are very good. It is the first time I am able to get images with such details.

To conclude, my TZ-3 telecentric has really improved my sight of the sun, and now if I want to go farther I should buy a very expensive narrow Ha filter, perhaps later.
In the next month, I will try the TZ3 on planetary images with my 300mm Meade SCT.

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Randy344/12/201711/12/201702:29

Rating:

Baader TZ3

I had been imaging the sun for a long time now but nobody made a telecentric 3x until now. My telescope is a F8 refractor and a 2x would only give me a F16 system while the available 4x would give me a F32 all but useless on most days where the seeing conditions are not perfect. Glad to see that Baader has answered the calls for a good telecentric lens of 3x.

What do you like about this item?:

I like the large aperture of the lens, the well made optics, and the fine machining of the lens system.

What do you dislike about this item?:

This is a bit picky but it could have better lens covers that fit a bit tighter.

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